Electromagnetic chuck



Jan. 12 1926. 1,569,599

W. ZEHNDER ELEGTROMAGNETIC CHUCK 'Filed oct. 5. 1921 sheets-sheet 1` $1-I l I-22 $1 Imi@ aan. 12 ,1926. 1,569,599

W. ZEHNDER ELECTROMAGNETIG CHUCK Filed OCT.. 5. 1921 2 Sheets-Sheet 2/25 3 5/ a l f7 a 25 ,9 M' ,ff/' 4 Patented 12, 192%.,

UNITED S'lA'laS WALTER ZEHNDER. F GRNIUHEN, SWILZERLAND.

ELECTRMrG-NETIC CHUCK.

Application tiled, Gctqber 5,

T all whom t may concern. f

Be it known that l, lVAL'rEn ZEHNDER, citizen of the Republic ofSwitzerland, residing at Granichen, Switzerland, have invented certainnew and useful Improvements in Electromagnetic Chucks, of which thefollowing is a. specification, reference beingl had therein to theaccompanying crawing..

This invention relates to improvements in electromagnetic chucks andparticularly to improvements in the plate for holding work pieces ofelectromagnetic chucks.

Most of the troubles with electromagnetic chucks arise from shortcircuits which originate from the fact that during the wet working of ablank the liquid, for instance the cooling wat-er, penetrates throughthe intermediate spaces between the pole pieces or between the polepieces and the tightening material which is inserted between the polepieces and passes into the interior of the electromagnetic chuck andgets in contact with the magnet coils. Electromagnetic chucks workingwith direct current are 'especially subjected to this danger because itis impossible to bring the non-magnetic material inserted in themagnetic plate, for instance the cast-in metal such as Zinc, intointimate contact with the iron and to maintain an intimate contact ofthat metal with the iron of the pole pieces. Therefore, after a shortworking period an appreciable air gap presents itself between thetightening material and the pole pieces through which gap the liquidleaks into the interior of the chuck. The heating up of the magneticilate contributes also to that leakage. With 'bucks worked withalternating current vhere metal cannot be cast in the spaces between thepole pieces for reasons due to the nature of the current, non-magneticmar terial such as gutta-percha, rubber, fibre and the like have beenpressed in between adjacent pole pieces. But also in this case gaps weresoon formed and the tightening material got detached from the iron ofthe pole pieces on account of chemical.y hygroscopical and thermalinliuences. rllhe utilization of electromagnetic chucks of the abovedescribed type prevented therefore the wet working of blanks, such asfor instance wet-grinding of pieces held by such a chuck.

The object of the present invention is a plate for holding work piecesin eleetro `.magnetic chucks com arising a pluralit" of v, o .Y ,y

pole pieces arranged side by side and nonniagnetic material beinginserted between the pole pieces and in which plate the above mentioneddisadvantages are overcome by arranging the pole pieces together withthe tightening material inserted between them in a frame chuck andpressing them tightly together and fixing them to said frame in theirpressed state. In chucks worked with direct current the pole pieces mayconsist of single piece of iron, for instance of a cast steel body, andthe intermediate spaces between two adjacent pole pieces may be filledup with brass sheets. With electromagnetic chucks worked withalternating current the pole pieces are built up of laminated dynamosheets and the intermediate spaces are filled up by a non-magnetic andnon-conducting material.

Several embodiments of the invention are 'shown by way of example on theaccompanying drawings, in which:

Fig. 1 is a section through a first constructional example along lineI-I' of Fig. 2;

Fig. 2 is a plan view in which part of the plate is broken off;

Fig. 3 is a cross-section along line III-III of Fig. 1;

Fig. 4: shows a modication of a detail;

F ig. 5 is a section of another constructional example along line VI-VIof Fig. 6;

Fig. G is a plan view with part of the top plate broken off and Fig. isa cross-section along line VIII--- VH1 of Fig G.

Referring to the Figs. 1 3 two longitudi nal bars 2 are rigidly .fixedby means of set screws 3 to the upper part of the chuck f casing 1 thatis open at its top. The sides of the two bars pointing towards eachother are J-'shaped and bars l of angle cross section and made of anon-magnetic material are inserted into said V-sliaped sides of the bars2. A cross piece 5 is inserted at each end of the bars 2 between saidbars and thus spaced from .each other by the plates aratinfcy plates andpole pieces 8.

'.7 ot nonmagnetie material and the whole space between'the twolongitudinal bars 2 or the bars el respectively and the two cross pieces5 are thus alternately lilled with sep- Previous to the second crI sspiece 5 being inserted and tixed a. very powertnl pressure is eX- ert-edupon the plates il and the pole pieces tl and then to the cross piece 5alter it has been brought in position a strong pressure in the directiontowards the already lined other cross piece 5 is applied wlierealter theplates i' and the dynamo sheets 8 are hcldtightly pressed together bythe cross pieces. T hen the second cross piece 5 is secured to 'thecasing l by means ot set screws G e Atering` tapped holes l oit thecasing` l. Set screwsll 'l'orlixing the longitudinal bars to the crosspieces serve to hold the tightlypressed parts together.

The magnets 9 are lier-ined by the coils l2 arranged around the coresif. The latter are als built up et laminated dynamo sheets and 'tornitogethtA th the yoke ifl one unit as may be seen Ytr l. ..:=e tween theends of the cores lil and the pole pieces S'there is provided a smallintermeliate space ot approximately t@ nnn. width tor permitting` o'tthe extension ot the parts .ansed by the heating and tor *lacilitatingerection. The dynamo sheets toi-ming the cores 'lf3 and the votre li ariheld together between the end sheets lli and clanipini;` pieces '17 bymeans ol screw bolts l5. rThe bolts l5 are paper insulated. Between theinner sides oic the longitudinal bars l1 and the inserted dynamo sheetsS an insertion ot paper is provided in order to prevent short circuitsbetween the dynamo sheets .t the sides thereof. r[his insertion Nervesat the same time as tightening' mate-- rial. rEhe yoke is held in atrame cured to the bottom ot the casing l by crews @ft tis not necessarythat thedynaino sheet.N rniinp; the pole pieces have the shape "ated inS but they may also be integral with the cores or with the dynamo sheetsof which the cores are termed as is shown in Fig'. Ll; ln this case thedyna'fno sheets are held. together by bolts arranged in the longitudinaldirection ol' the chuck instead ot the bolts l5 arranged in thetransverse direction as shown in Fig. To this end holes 1Q (Fig. Zl) areprovided in 'th dynamo sheets. rlhe dynamo sheets site nated between thesets ol1 sheets torniiino3 each core are not provided with the downwardextension as illustrated in Fig'. l but are ot the saine shape thedynamo sheets S in Fig. 3. The sheets 18 abut against a Common yoke lilwhich is built up of dynathe longitudinal in this case. Thisconstruction is especially suited for holding` small work pieces, as 1norder to be held by the chuck a work piece has to lfiridge over andconnect magnetically t o separated by an interme- 'wo pole pieces o ydiate plate 7. ln this constrnctional examile the volte lll is clampedin between two onjjfitudinal supporting` beams which are suspended 'tromthe plate consisting oit' the pole pieces 8 and the interniediate parts7 by means oi screw bolts 26.

In the chuclts according' to the invention no gaps between the polepieces and the silvacinc material can itorm then'iselves and these.clinchs are therefore particularly suited Ytor the wet-working o't workpieces.

clain'i:

l. ln :in electromagnetic chuck. a (lat, composite plate composed olEsets ol laminations ol dynamo sheet alternating with nonniagi'wlicmaterial. said laniinations ari'ang'ed transversely ol the flat plate.said plate having;v opposite wedge-shaped edges, n'teans at the ends otthe plate to hold the composite plate con'ipressed with a 'orcosnliicient to prevent the passage ot water between the lz-rminationsunder all conditions ot Xpansion and contraction incident to the use otthe chuck. and longitudinal hars having` V-shaped recesses in whicn thewedge-shaped edges of the plaie litand are held wat er ti gjhtf 2. ln anelectronnignctic clinch. :i casing open at its top, a worloholdine`col'i'iposite plater 'forming a cover lor said casing' and cons ine` ofgroups o1" vertical laininations alternating' with non-'magneticmaterial arranged transversely ot' said'plal'e and harinc` wedge-shapedends, means secured to said casing; to maintain the laminat-ions ot heplate under compression, longfilviulinal .i havi g' V-shaped slots intowhich the i edge-shaped ends et the laminatious llt. iid barssecnred tosaid ineans and the cas n'. laminated niagnetcores in the casiucY in becath said plate, windings on the. cores and a yolte nieniber 'tor thecores.

ln testin'iony whereo'li l atilx my signature.

